Laser sealing of dissimilar polymers for manufacturing packaging products

Abstract

Laser sealing of thin/dissimilar polymers has the potential to become a superior technique that could be applied to a range of general packaging products. Upon successfully applying laser sealing to such products could result to faster throughputs, shorter lead-times, lower energy consumption, and in turn, a competitive advantage for packaging product manufacturers. The work herein is focused on the physical laser-material interaction resulting from laser sealing a 42 μm high density linear polyethylene (HDLPE) film to a 1 mm polypropylene (PP) substrate. The paper also details a comparison of laser sealing with the conventional pressure/heat sealing process. The results showed that a 10.6 μm wavelength laser, the required parameters to produce an acceptable seal were: 60 W of laser power, 1.67 mm spot diameter, and a traverse speed of 300 mm/min using a double pass. Microstructural study showed sufficient bonding of the laser sealed region with an amorphous zone. Defects were also present in various areas when comparing the results of laser sealing to the conventional sealing process. Nonetheless, the peel strength tests showed laser sealing required up to 30% higher force than the conventionally sealed HDLPE film to PP substrate. A steady-state finite element model of the laser sealing process showed distribution of heat at the film/seal activation temperature. This confirmed the sealing temperature at the laser-polymer interaction zone to gain further understanding of the new process as a whole.